In everyday life, fast one-, two-, and multi-choice decisions are common. Rapid decisions must be made based on any number of sources of information, often in the face of quickly changing conditions. The paramount aim of the proposed research is to move a set of Cognitive Psychology theories to practical issues. The plan is to use the theories to develop tools with which to measure the basic, elemental processes by which rapid decisions are made. Currently, modern cognitive theories have had little impact on neuropsychological testing. The goal of the proposed research is to begin to change this by providing a coherent, theory-based account of rapid one-, two-, and multi-choice decisions. The Cognitive Psychology models to be used are designed to explain the accuracy and speed of simple decisions in the research domains of perception and memory and to bridge to the practical domains of cognition and driving, and cognition and aging. For example, in driving, deciding to slow at the onset of another car's brake lights is a one-choice decision; deciding whether a patch of light is darker or brighter than the background is a two-choice decision; rating the confidence in whether a word or picture was studied earlier is a multi-choice decision. The three models we will use, one for one-choice decisions, one for two-choice decisions, and one for multi-choice decisions, use diffusion processes and share foundational properties. Each divides processing into similar components: the quality of the information upon which a decision is based, the criteria that determine how much information must be available in order to make a decision, the encoding and memory-access processes that make the needed information available, and the response execution processes that make a decision overt. Central to our aims, the models allow examination of the particular, moment-by-moment, processes that take place between the presentation of a stimulus and the response to it. The research will investigate these processes for college-age adults and elderly adults (ages 60-74). The planned approach is to develop and test new models for one- and multi-choice decisions in a variety of domains. The one-choice model will be tested in experiments that involve simulated driving and perceptual tasks that have been used to assess the effects of sleep deprivation on cognition. The multi-choice model will be tested in the domains of memory and perceptual judgments. In both cases, planned experiments will allow comparisons of the two models to a currently well-validated two-choice model. The eventual goal of the proposed research is the development of neuropsychological tests that can be used to assess the impacts on cognition of, for example, concussion, aging, and chemotherapy. The research will be innovative in that the one-, two- and multi-choice models have not previously been used in the diagnosis of cognitive impairments or in the tracking of recovery from them.